Investigation of human hair cuticle structure by microdiffraction: direct observation of cell membrane complex swelling

The cuticle of mammalian hair fibres protects the core of the fibre against physical and chemical stress. The structure and some of the properties of the cuticle have been extensively studied by electron microscopy. However, there is still a need for a less invasive structural probe. For this purpos e, microdiffraction experiments have been carried out on human hair samples showing a characteristic small-angle X-ray scattering pattern for the cuti cle. This pattern has been assigned to the cell membrane complex (CMC) betw een each cuticle scale. Using a simple model of the electron density within the CMC, values have been derived for the average thickness of the beta- a nd delta -layers which are close to those obtained by electron microscopy. In order to illustrate the potentialities of microdiffraction in studying t he properties of the cuticle, the effect of water sorption has been monitor ed. Using the intensity modelling described above, a 10% swelling of the de lta -layer's thickness has been observed. This study shows that structural modifications of the CMC by physical or chemical stress can be followed dir ectly on the cuticle of human hair fibres by microdiffraction analysis. (C) 2001 Elsevier Science B.V. All rights reserved.